Pipe coupling

A pipe coupling including a socket and a plug which respectively have front end portions which can be engaged with each other, as well as rear end portions connected with pipes, wherein

• the socket comprises a socket body having an open end where an axial bore for receiving the plug is opened, at least one lock ball which can be moved between a lock position where the lock ball partially projects into the axial bore and an unlock position where the lock ball is retracted thereby making the plug movable in the axial-direction, and a sleeve slidably mounted on the socket body and capable of holding the lock ball at the lock position;
• the plug has a groove in which the lock ball can be engaged,
• the socket body has a front end portion adjacent to the open end, and a lock ball engage hole which is formed at the front end portion, receives the lock ball movably in an axial direction and a radial direction, can retract the ball from the lock position where the lock ball partially projects into the axial bore, and is elongated in the axial direction,
• the sleeve is mounted on the outer circumference of the socket body to be rotatable about an axis thereof, and has an inner circumferential surface, a press portion which is formed on the inner circumferential surface and presses the lock ball located at a position close to the open end in the lock ball engage hole toward the lock position, a press release recessed portion capable of retracting the lock ball to the unlock position, and a large diameter portion arranged axially adjacent to the press portion and the press release recessed portion and capable of retracting the lock ball located at a position distant from the open end to the unlock position,
• the pipe coupling further comprises a sleeve rotation restricting mechanism for restricting a rotation range of the sleeve to an angular range between a press position where the press portion opposes the lock ball and a press release position where the press release recessed portion opposes to the lock ball, a collar movably contained in the large diameter portion, and a spring for urging the sleeve toward the press position and for urging the collar toward the open end, and
• one of the socket body and the sleeve comprises at least one projecting portion, and another one comprises a first recessed portion capable of receiving the projecting portion along an axial direction and a second recessed portion communicating with the first recessed portion, wherein the socket body and the sleeve are stopped so as to prevent relative movement in a circumferential direction against the spring urging in the circumferential direction and an axial direction when the projecting portion is engaged with the first recessed portion, and movement in an axial direction between said socket body and the sleeve standing against the spring urging in the axial direction is disabled and relative rotation standing against the spring urging in the circumferential direction is allowed when the projecting portion is contained in the second recessed portion.